Abstract: Executive Order 13112 requires federal agencies to report invasive species costs to the National Invasive Species Counsel (NISC) annually. NISC then reports to Congress to increase awareness of invasive species and encourage inter-agency cooperation. Since 2005, the US Army Corps of Engineers (USACE) has provided an annual estimate for the Civil Works (CW) business lines. Traditionally, USACE estimates have been informed by broad assumptions, as many invasive species costs are not itemized. This study sought to develop a method to improve these estimates. A demonstration analysis was conducted for the Chicago District Navigation Business Line and was used to inform recommendations for a nation-wide analysis. The demonstration revealed invasive species-related costs represent about 0.2% ($64,000) of the district’s Navigation Business Line. Invasive species costs are subject to many variables, such as the type, prevalence, and impact of invasive species, as well as the number and type of navigation projects. The Chicago District results are not presumed to be indicative of other districts’ invasive species costs. Rather, the demonstration informed the development of an invasive species cost estimating method that can adapted for each CW business line, as well as variations in invasive species and projects across geographic regions. This report describes the demonstration analysis and presents a defensible framework for quantifying the costs of invasive species to the USACE CW program.